Genus/Species
formerly genus Agkistrodon
Species
- 1. Hypnale hypnale
- 2. Hypnale nepa
- 3. Hypnale walli
Taxonomy
Common names
- 1. Hump-nosed viper, Indische Nasenotter
- 2. Sri Lankan hump-nosed viper, Ceylon-Nasenotter
- 3. Wall's hump-nosed viper
Distribution
Sri Lanka and the southern region of the Western Ghats in India. See link "Distribution" at the top of the page for detailed information. Map 61 Hypnale spp.
Biology
The three species are difficult to distinguish from each other. As with Calloselasma rhodostoma and Deinagkistrodon acutus they were previously included among the genus Agkistrodon, and their appearance is very similar to those species. Clearly distinct, triangular, flat head. Tapering snout; H. nepa and H. walli have a wart-like protuberance on the tip of the snout. Colouring and markings are very variable, with basic shades of light to dark grey or brown, sometimes with small, dark, semicircular blotches along the spine.
Predominantly ground-dwelling and nocturnal. H. hypnale is the largest species but barely reaches more than 50 cm. It is very common in Sri Lanka and inhabits the most varied climate zones. It lives primarily in forests and grasslands as well as in different agricultural areas (rubber, coffee, tea, coconut, cocoa and banana plantations), at altitudes of up to 1,250 m above sea level. H. walli found exclusively in rainforests, H. nepa also in other forests.
During the day they often lie under leaf litter, fallen wood or stones. When threatened they coil their body, vibrate the tip of their tail and raise their upper body slightly. From this defensive position, H. hypnale in particular strikes without hesitation.
Risk
Fatalities very rare. H. hypnale, as the most dangerous species of its genus, causes the majority of venomous snakebites in Sri Lanka. H. hypnale bites can cause not only local effects, as is common with H. nepa and H. walli, but also severe systemic effects (Warrell, pers. comm.).
Literature (biological)
Gloyd and Conant 1989, Gumprecht et al. 2004, De Silva 1990